1. Field of the Invention
The present invention relates in general to data processing systems and, in particular, to a data processing system and method for disabling a portable computer when the portable computer is outside an authorized, geographical area. Still more particularly, the present invention relates to a data processing system and method for disabling a portable computer when the portable computer is outside an authorized, geographical area utilizing a global positioning system device.
2. Description of the Related Art
Personal computer systems are well known in the art. They have attained widespread use for providing computer power to many segments of today's modern society. Personal computers (PCs) may be defined as a desktop, floor standing, or portable microcomputer that includes a system unit having a central processing unit (CPU) and associated volatile and non-volatile memory, including random access memory (RAM) and basic input/output system read only memory (BIOS ROM), a system monitor, a keyboard, one or more flexible diskette drives, a CD-ROM drive, a fixed disk storage drive (also known as a "hard drive"), a pointing device such as, a mouse, and an optional network interface adapter. One of the distinguishing characteristics of these systems is the use of a motherboard or system planar to electrically connect these components together. Examples of such personal computer systems are IBM's PC 300 series, Aptiva series, and Intellistation series.
Portable computers are one of the most stolen electronic devices on the market today. After being stolen, a portable computer is typically removed from its area of origin and resold in another area. This prevents local police from easily recovering the computer.
In one known system for protecting portable computers, the portable computer is capable of receiving a cellular telephone signal causing the activation of a beacon unit. Once the owner of a portable computer discovers the computer is stolen, the owner of the system may cause the transmission of a beacon signal. When the portable computer receives the beacon signal, it activates a security program to protect the computer's files. The beacon signal is transmitted to the portable computer utilizing cellular telephone technology regardless of the physical location of the portable computer. This system requires the owner of the portable to first determine that the portable has been stolen, and then take steps to activate the beacon signal. A significant amount of time may pass before the owner discovers the portable computer missing. The thief will likely have already accessed the portable's files and data, and may have been able to disable the beacon unit within the portable prior to the owner causing the transmission of the beacon signal.
Known systems exist for tracking the physical location of vehicles. Many of the systems utilize the Global Positioning System to determine a physical location of a particular vehicle. The Global Positioning System (GPS) is an accurate, three-dimensional navigation system. The GPS includes a constellation of twenty-one satellites and three spares that orbit the earth twice a day at an altitude of 10,898 miles. The satellites orbit the earth in six overlapping orbital planes which are based on the equatorial plane of the earth. The orbits of the satellites enable any GPS receiver near the surface of the earth to receive signals from at least four satellites at any one time, although precise position information can be obtained with only three satellites. A GPS receiver can be located in mobile units such as aircraft or ground vehicles to enable them to precisely locate their global positions. Each satellite continuously broadcasts pseudo-random codes at L-band frequencies, L1 at 1575.42 MHz and L2 at 1227.6 Mhz. Each satellite broadcasts a slightly different signal and each satellite broadcasts two types of signals. One of these signals is referred to as C/A code, which is a signal that can be received by civilian type GPS receivers. The other signal is referred to as P code, which is a signal that can be received only by military type GPS receivers.
Ground stations on the earth receive transmissions from the satellites. These transmissions are analyzed and GPS time is compared with universal standard time at the ground stations. Corrections are transmitted to receivers in each of the satellites from the ground station. The signals which include the time the signal left the satellite, are broadcast from the satellites and decoded by the GPS receiver using triangulation techniques provided by software in the receiver to determine the location. Specifically, the interval between the transmission and the reception of the satellite signal is used to calculate the unit's distance from each of the satellites being used. Those distances are used in the algorithms to compute the receiver's position.
Therefore a need exists for a data processing system and method for disabling a portable computer when it has been moved outside an authorized, geographical area.